It has been previously shown that several chemical commonly found in commercially available sunscreens were capable of eliciting phototoxic responses when applied to human skin and exposed to UVA (320-400 nm). The purpose of this project is to examine the biochemical and cellular effects of several of these sunscreen agents alone and in conjunction with UV light on mammalian cells. The sunscreen agents chosen for the study include p-aminobenzoic acid, Escalol 506, Escalol 507, and dihydroxyacetone (DHA). The effects of each of the agents on DNA repair synthesis in mouse 10T 1/2 fibroblasts has been examined and it was determined that both Escalol 506 and Escalol 507 induced DNA repair activity. In addition, these compounds are being tested in an in vitro transformation system. Preliminary evidence indicates that DHA is a potent inducer of in vitro cell transformation. Mammalian and bacterial mutation studies are in progress in order to determine the mutagenicity of each of these compounds as well as the relationship of mutagenicity to DNA repair induction and cellular transformation.